<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css" integrity="sha384-HSMxcRTRxnN+Bdg0JdbxYKrThecOKuH5zCYotlSAcp1+c8xmyTe9GYg1l9a69psu" crossorigin="anonymous">
  <title>Document</title>
</head>
<body>
  <h1 class="text-center text-danger">我是标题</h1>
  <div class="btn-group" role="group" aria-label="...">
    <button type="button" class="btn btn-info">Info</button>
    <button type="button" class="btn btn-danger">Danger</button>
    <button type="button" class="btn btn-default">Right</button>
  </div>
  <form>
    <div class="form-group">
      <label for="exampleInputEmail1">Email address</label>
      <input type="email" class="form-control" id="exampleInputEmail1" placeholder="Email">
    </div>
    <div class="form-group">
      <label for="exampleInputPassword1">Password</label>
      <input type="password" class="form-control" id="exampleInputPassword1" placeholder="Password">
    </div>
    <div class="form-group">
      <label for="exampleInputFile">File input</label>
      <input type="file" id="exampleInputFile">
      <p class="help-block">Example block-level help text here.</p>
    </div>
    <div class="checkbox">
      <label>
        <input type="checkbox"> Check me out
      </label>
    </div>
    <button type="submit" class="btn btn-default">Submit</button>
  </form>
  <table class="table table-bordered">
    <tr>
      <td>1</td>
      <td>2</td>
      <td>3</td>
    </tr>
    <tr>
      <td>1</td>
      <td>2</td>
      <td>3</td>
    </tr>
  </table>
</body>
</html>